Method of preparing molds for dental castings



April. 27 1926. 1 582291 F. C. MONTUORI METHOD OF PREPARING MOLIIDS FORDENTAL CASTINGS original Filed July 30. 1924 gwuentou VWM Patented Apr.27, 1926.

UNITED STATES 1,582,294 PATENT OFFICE.

FELIX C. MONTUORI, OF WASHINGTON, DISTRICT OF COLUMBIA.

METHOD OF PREPARING MOLDS FOR DENTAL CASTINGS.

Original application filed July 30, 1924, Serial No. 729,186. Dividedand this application filed April 21,

To all whom it may concern:

Be it known that I, FELIX C. MoNTUonI, a citizen of the United States,residing at- W'ashington', in the District of Columbia, have inventedcertain new-and useful Improvements in Methods of Preparing Molds forDental Castings, of which the following is a specification.

My invention relates to a method of preparing molds for dental castings,and has for its object to properly regulate the elimination of the waxpattern and prepare the mold for casting without accident, such as thecracking of the mold from excessive or too rapidly applied heat, or thebursting of it from rapidly generated internal vapor or gaseouspressures; and to make the preparation of the molds rapid, certain as toresult, convenient and economical of time and labor.

In the preparation of a flask for dental castings to make it ready forthe casting of a metal object, such as metallic dental filling, theusual procedure is to form a wax pattern exactly similar in size. andshape to the desired casting, and then support this pattern on a wire,and properly arrange these parts in the middle part of the flask,- andthen pour or place into the flask around the pattern and its supportingwire, a suitable mold material or investment, such as silica and plasteror other investing refractory material or compound.

It is now necessary to have this investing material set and dried, andthe pattern entirely removed so as to leave a mold suitable for thereception of the casting. At a suitable time, after the investment isset, the wire is removed to leave a sprue leading from the exterior ofthe flask to the mold cavity.

My improvement comes into operation for the purpose of so drying out theinvestment and melting and dissipating into vapor or gas the waxpattern.

This last step has usually been performed.

by the aid of gas flames turned up more. or

less high or by other available sources of heat such as electric ovensor mufiles, and much difliculty has been experienced from applying toomuch heat to the flask initially, and trouble has been involved in fromtime to time increasing the heat as the drying of theflask and removalof the pattern proceeded. The ap'plication'of too much heat at thebeginning has resulted in the cracking Serial No. 24,760.

.ofthe investment from uneven drying or the bursting of it from suddenlycreated inthe mold of investment material as de-' scribed, an electricheater or heating conductor adapted to have the investment materialmolded directly within it, the electric conductor being suitablyinsulated from the investment material, then a suitable electric currentis applied through said conductor to gradually and evenly dry out theinvestment and dissipate the pattern in the desired manner, and so as toleave the mold, in its interior parts, entirely free from cracks orimperfections. The usual incandescent lighting current is suitable forthis purpose when passed through the conductor within which the mold hasbeen prepared.

\Vith such objects in view, as well as other advantages which may beincident to the use of the improvements, the invention consists in thesteps of procedure and combinations thereof hereinafter set forth andclaimed, with the understanding that variations may be made inproportions and arrangement without departing from the nature and scopeof the invention. v

In order to make the invention more clearly understood there are shownin the'accompanying drawings means for carrying the same intopracticaleftect, without limitingthe improvement, in its usefulapplications, to the particular constructions which, for the purpose ofexplanation, have been made the subject of illustration.

In said drawings: v

Fig. 1 is a vertical sectional view of a flask for dental castingssuitable for use in carrying out my invention.

Fig. 2 is a vertical section of the same after the mold has beenprepared for heating.

Fig. 3 is a plan view showing the flaskconductor attached in an electricheating circuit. i

Fig. 4 is a vertical section showing the mold completed and empty, andthe investment dried, ready for the casting o eration.

Referring to the drawing, A indicates a flask which comprises interiorand exterior walls 1 and 2 which are somewhat spaced apart from eachother.

On the exterior surface of the wall 1 is preferably applied a sheet ofmica 3, and exterior to this mica is arranged an electric heatingelement 4, such as the coils of a resistance wire, this wire being ofround or flattened cross-section. At the outer side of the unit 4 isarranged another sheet of mica 5 extending all around the outer side ofsaid inner coil. At the outer side of this second layer of mica isarranged a second electricheating unit or coil 6, which may be connectedwith the coil 4 either in series or parallel. The two ends a, b, of thistwo-part coil 4, 6, are led out through the outer wall 2 of the flask bymeans of porcelain or other refractory insulating bushings 7 and haveterminals suitable to be applied tocorresponding terminals of anelectric circuit or source of suitable electric tension or power.

The spaces between said layers of mica and the exterior wall 2 of theflask are solidly filled with a highly refractory and insulatingmaterial 10, such as porcelain or a composition forming a kind ofartificial stone or equivalent heat and water resisting and electricinsulating compound or material, eompositions for this purpose beingwell known and available.

The lower edge of the inner wall 1 preferably terminates in a flange 8which is more material to be poured or placed within the I flask and atthe same time within the area defined by the heating element 4, 6 in themold forming operation. This material or investment may be silica andplaster or other suitable refractory material or compound 11,

in which may be formed the mold cavity 12 by means of the pattern 13supported by the wire 14 on a suitable base 14', the wire forming thesprue 15, all as above described. The wire 14 may be removed before theapplication of the electric current and the heating of the flask, or itmay be left in place during such operation, as may be found mostconvenient and desirable.

After the use of the flask as above set forth and the completion of thecasting operation the material 11 may be broken or washed out of thesame, for the repeated using of the flask for different castings in theusual manner.

In Fig. 3 is shown a stand 16 for electrical terminals 17 with which theterminals a and b may be brought into contact for the passage of theelectric current through the electrical conducting and resistance orrheostat coils 4 and 6.

After the flask has been completed for the production of a particularcasting I do or may proceed with the casting process as set forth in myPatent No. 1,490,625, granted April 15, 1924.

This application is a required division of my application Serial No.729,186, filed July 30, 1924, in which is claimed my improved apparatus,and I do not herein claim said apparatus.

What is claimed is: The method of preparing molds for dental castingswhich consists in pouring the investment material around a fusiblepattern and a spruc former" placed within a surrounding electric heatingelement electrically insulated from the said investment material, andthen passing an electric current through said heating element, therebyfusing and dissipating the pattern, thus preparing the mold cavity andalso gradually drying the investment material for the casting operation.

In testimony whereof I aflix my signature.

FELIX C. MONTUQRI.

